Parabolic Reflector Antenna

Parabolic Reflector Antenna

All of you would have seen the dish antennas on roof tops being used for direct to home satellite television reception. They are parabolic reflector antennas. In amateur radio they are used to receive and transmit signals to the Qatar Oscar 100, the only Geostationary Amateur Radio satellite in orbit at present. History tells us that amateur radio astronomer Grote Reber built a 9 meter parabolic radio telescope antenna in his backyard in 1937. From local WhatsApp groups and qrz.com I can understand many of the local Ham Radio operators are also amateur astronomers, though I am not sure how many of them are amateur radio astronomers!

As the name implies, parabolic reflector antenna uses a parabolic reflector to direct radio waves. Many of you would be familiar with the parabolic reflectors in the torch lights. Parabolic antennas have high gain and produce very narrow beams compared to any other type of antenna. The parabolic reflector has to be much larger than the operating wavelength. Hence it is practical only at UHF and SHF ranges so that conveniently sized reflectors can be made. Qatar Oscar 100 Geostationary Amateur Radio Satellite uplink works in UHF range and downlink in SHF range.

Parabolic reflector antenna has a metal parabolic reflector and a small feed antenna suspended in front at the focal point of the parabolic reflector. Radio waves being received by the parabolic reflector are focussed on to the small antenna which receives the signals and transfers them to the radio through the feed line. During transmission, the reverse process occurs and the parabolic reflector sends out the beam of radio waves.